Antibodies and Memory Cells Role After Different Pneumococcal Vaccines in HIV Adults

Streptococcus pneumoniae is a cause of high morbidity and mortality in HIV-positive subjects, representing the leading etiological agent of severe bacterial pneumonia. International guidelines recommend that HIV positive patients aged \>=19 years, who are 13-valent conjugate vaccine (PCV13) naïve, should receive a single dose of PCV13. Pneumococcal polysaccharide vaccine 23-valent (PPV23) should be given \>=8 weeks after indicated dose of PCV13, and a second dose of PPV23 should be given 5 years later. For those who previously received PPV23, PCV13 should be administered \>=1 year after the last PPV23 dose. HIV infection affects humoral immunity both through reduced T-cell help and changes in the B-cell compartment. Neither amount of circulating memory B cells nor their functions are restored by antiretroviral therapy: this may affect antibody mediated immunity, even in well-treated HIV patients. In asplenic childrens a single dose of PCV13 seems sufficient to restore the pool of anti-pneumococcal polysaccharides IgG memory B cells. In adults, it has been reported that a single dose of 7-valent pneumococcal conjugate vaccine induces significant increases in serotype-specific memory B-cell populations, conversely, immunization with PPV23 seems to decrease memory B-cell frequency. However, data on immunological response after PCV13 in HIV positive adults are still scanty and the optimal pneumococcal prophylaxis strategy needs further investigation. Number of PCV13 doses is actually demanded to clinical judgment for each patient; also current Italian indications recommend at least one dose, but till 3 doses seem to be suggested for immunocompromised patients. Present study aims to investigate short and long term immunological response after different standard vaccine schedule and to evaluate pneumococcal nasopharyngeal colonization in vaccinated patients.